Abstract

Although the southern Front Range in Colorado Springs and Manitou Springs contains a near-complete record of Rocky Mountains geological evolution from Proterozoic to Present, there nevertheless are persistent geological problems that have eluded understanding for as much as 125 years. In keeping with the 2013 GSA Annual Meeting theme, “Celebrating Advances in Geoscience,” this field trip visits long-known elements of Front Range geology that merit reexamination within the context of new paleoenvironmental and geochronology data. Of note are: (1) the Great Unconformity and its chemically weathered substrate that correspond to a time of profound changes in global ocean chemistry; (2) lower Paleozoic strata that record sea-level fluctuations, attributable in part to regional tectonism; (3) an array of granite-hosted sandstone dikes, for which a new emplacement model is proposed; and (4) the Front Range monocline at Garden of the Gods Park, examined from the standpoint of its temporal evolution, newly bracketed by results of 40Ar/39Ar age analysis of illite generated by shear upon bedding-parallel faults.

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The Rocky Mountain Region has been the subject of continuous, exhaustive scientific work since the first organized geologic trips to the area began in the 1860s. Despite almost 150 years of scrutiny, the region's magnificent geology continues to challenge, perplex, and astound modern geoscientists. It is a testing ground for geologists and for big geologic ideas. This volume, prepared for the 2013 GSA Annual Meeting in Denver, Colorado, serves both as a progress report on what we have learned over those years of study and a guide to forthcoming scientific questions about the region. The guide's fourteen chapters, which span the region's 1.7-billion-year history, give a retrospective glimpse of early geologic ideas being forged, bring the latest mapping and analytical results from classic locations, and introduce techniques that will form the bedrock of our geologic understanding in the years to come.